From a9f6dbc68b8f09d57b5ac2d9fa08f430a322db2f Mon Sep 17 00:00:00 2001
From: Brian Popow <popow@gmx.de>
Date: Sun, 29 Mar 2026 17:19:46 +0200
Subject: [PATCH] Add compression to exr metadata

---
 src/ImageSharp/Formats/Exr/ExrDecoderCore.cs  |  1 +
 src/ImageSharp/Formats/Exr/ExrMetadata.cs     |  7 ++++++-
 .../Formats/Exr/ExrMetadataTests.cs           | 20 ++++++++++++++++++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/ImageSharp/Formats/Exr/ExrDecoderCore.cs b/src/ImageSharp/Formats/Exr/ExrDecoderCore.cs
index 1127b146c5..8a893c3c83 100644
--- a/src/ImageSharp/Formats/Exr/ExrDecoderCore.cs
+++ b/src/ImageSharp/Formats/Exr/ExrDecoderCore.cs
@@ -496,6 +496,7 @@ internal sealed class ExrDecoderCore : ImageDecoderCore
         this.exrMetadata = this.metadata.GetExrMetadata();
         this.exrMetadata.PixelType = this.PixelType;
         this.exrMetadata.ImageDataType = this.ImageDataType;
+        this.exrMetadata.Compression = this.Compression;
 
         return this.HeaderAttributes;
     }
diff --git a/src/ImageSharp/Formats/Exr/ExrMetadata.cs b/src/ImageSharp/Formats/Exr/ExrMetadata.cs
index f618b6d6f9..1fa724657f 100644
--- a/src/ImageSharp/Formats/Exr/ExrMetadata.cs
+++ b/src/ImageSharp/Formats/Exr/ExrMetadata.cs
@@ -35,6 +35,11 @@ public class ExrMetadata : IFormatMetadata<ExrMetadata>
     /// </summary>
     public ExrImageDataType ImageDataType { get; set; } = ExrImageDataType.Unknown;
 
+    /// <summary>
+    /// Gets or sets the compression method.
+    /// </summary>
+    public ExrCompression Compression { get; set; } = ExrCompression.None;
+
     /// <inheritdoc/>
     public PixelTypeInfo GetPixelTypeInfo()
     {
@@ -92,7 +97,7 @@ public class ExrMetadata : IFormatMetadata<ExrMetadata>
     /// <inheritdoc/>
     public FormatConnectingMetadata ToFormatConnectingMetadata() => new()
     {
-        EncodingType = EncodingType.Lossless,
+        EncodingType = this.Compression is ExrCompression.B44 or ExrCompression.B44A or ExrCompression.Pxr24 ? EncodingType.Lossy : EncodingType.Lossless,
         PixelTypeInfo = this.GetPixelTypeInfo()
     };
 
diff --git a/tests/ImageSharp.Tests/Formats/Exr/ExrMetadataTests.cs b/tests/ImageSharp.Tests/Formats/Exr/ExrMetadataTests.cs
index c94b6dce54..2cbbf0ec31 100644
--- a/tests/ImageSharp.Tests/Formats/Exr/ExrMetadataTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Exr/ExrMetadataTests.cs
@@ -13,14 +13,16 @@ public class ExrMetadataTests
     public void CloneIsDeep()
     {
         ExrMetadata meta = new()
-        { ImageDataType = ExrImageDataType.Rgb, PixelType = ExrPixelType.Half };
+        { ImageDataType = ExrImageDataType.Rgb, PixelType = ExrPixelType.Half, Compression = ExrCompression.None };
         ExrMetadata clone = (ExrMetadata)meta.DeepClone();
 
         clone.ImageDataType = ExrImageDataType.Gray;
         clone.PixelType = ExrPixelType.Float;
+        clone.Compression = ExrCompression.Zip;
 
         Assert.False(meta.ImageDataType.Equals(clone.ImageDataType));
         Assert.False(meta.PixelType.Equals(clone.PixelType));
+        Assert.False(meta.Compression.Equals(clone.Compression));
     }
 
     [Theory]
@@ -67,4 +69,20 @@ public class ExrMetadataTests
         Assert.NotNull(metadata);
         Assert.Equal(expectedImageDataType, metadata.ImageDataType);
     }
+
+    [Theory]
+    [InlineData(TestImages.Exr.UncompressedRgba, ExrCompression.None)]
+    [InlineData(TestImages.Exr.B44, ExrCompression.B44)]
+    [InlineData(TestImages.Exr.Rle, ExrCompression.RunLengthEncoded)]
+    public void Identify_DetectsCorrectCompression(string imagePath, ExrCompression expectedCompression)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using MemoryStream stream = new(testFile.Bytes, false);
+        ImageInfo imageInfo = Image.Identify(stream);
+
+        Assert.NotNull(imageInfo);
+        ExrMetadata metadata = imageInfo.Metadata.GetExrMetadata();
+        Assert.NotNull(metadata);
+        Assert.Equal(expectedCompression, metadata.Compression);
+    }
 }